This fixes a number of cases where we capitalized error messages or
printed a full-stop, and corrects "Dwarf" to "DWARF".

bfd/
	* dwarf2.c, * elf-attrs.c, * elf-eh-frame.c, * elf.c, * elf32-gen.c,
	* elflink.c: Standardize error/warning messages.  Replace use of
	linker callback einfo with _bfd_error_handler when possible.
ld/
	* testsuite/ld-elf/indirect.exp,
	* testsuite/ld-elf/pr22649-2ab-mips.msg,
	* testsuite/ld-elf/pr22649-2cd-mips.msg,
	* testsuite/ld-elf/pr22649.msg,
	* testsuite/ld-elf/tls_common.exp,
	* testsuite/ld-elfcomm/elfcomm.exp,
	* testsuite/ld-arm/attr-merge-incompatible.d,
	* testsuite/ld-tic6x/attr-compatibility-gnu-other.d,
	* testsuite/ld-tic6x/attr-compatibility-other-gnu.d,
	* testsuite/ld-tic6x/attr-compatibility-other-other.d,
	* testsuite/ld-i386/warn1.d: Update expected error/warning messages.